Method and apparatus for performing channel detection

ABSTRACT

A technique for performing channel detection in a device such as a television signal receiver is capable of quickly determining the analog and/or digital broadcast channels available in a given area. According to an exemplary embodiment, a method for performing channel detection includes tuning a first frequency channel, determining whether a signal parameter associated with the first frequency channel exceeds a predetermined threshold, and enabling a first channel acquisition operation responsive to determining that the signal parameter exceeds the predetermined threshold.

The present invention generally relates to channel detection, and moreparticularly, to a technique for performing channel detection in devicessuch as a television signal receiver that is capable of quicklydetermining the analog and/or digital broadcast channels available in agiven area.

Certain devices such as television signal receivers may be capable ofreceiving and processing analog and/or digital broadcast signals. Withsuch devices, a user-initiated channel setup process may be performed inorder to determine the analog and/or digital broadcast channelsavailable in a given area. Such a channel setup process may for examplerequire a search for both analog broadcast channels, such as NationalTelevision Standards Committee (NTSC) channels, and digital broadcastchannels, such as Advanced Television Standards Committee (ATSC)channels.

According to one conventional channel setup process, a frequency channelis tuned, and a digital channel acquisition operation is performed. Ifthe digital channel acquisition operation is successful (i.e., a validdigital broadcast channel is detected on the tuned frequency channel),then the digital broadcast channel is added to a list of valid broadcastchannels. Alteratively, if the digital channel acquisition operation isunsuccessful (i.e., a valid digital broadcast channel is not detected onthe tuned frequency channel), then the digital channel acquisitionoperation is terminated, and an analog channel acquisition operation isperformed. If the analog channel acquisition operation is successful(i.e., a valid analog broadcast channel is detected on the tunedfrequency channel), then the analog broadcast channel is added to thelist of valid broadcast channels. Alternatively, if the analog channelacquisition operation is unsuccessful (i.e., a valid analog broadcastchannel is not detected on the tuned frequency channel), then the analogchannel acquisition operation is terminated, and another frequencychannel is tuned where the digital and analog channel acquisitionoperations are repeated.

With the aforementioned channel setup process, the longest amount oftime in searching a particular frequency channel occurs when no signalis present on that frequency channel since both the digital and analogchannel acquisition operations must be performed in order to gainconfidence that there is really no signal present. In such cases, theoverall time required for the channel setup process may become undulyprotracted, and therefore unacceptable to many users.

Accordingly, there is a need for a technique for performing channeldetection in devices such as a television signal receiver which avoidsthe foregoing problems, and is capable of quickly determining the analogand/or digital broadcast channels available in a given area. The presentinvention addresses these and other issues.

In accordance with an aspect of the present invention, a method forperforming channel detection is disclosed. According to an exemplaryembodiment, the method comprises steps of tuning a first frequencychannel, determining whether a signal parameter associated with saidfirst frequency channel exceeds a predetermined threshold, and enablinga first channel acquisition operation responsive to determining thatsaid signal parameter exceeds said predetermined threshold.

In accordance with another aspect of the present invention, an apparatusfor performing channel detection is disclosed. According to an exemplaryembodiment, the apparatus comprises tuning means for tuning a firstfrequency channel. Processing means determine whether a signal parameterassociated with the first frequency channel exceeds a predeterminedthreshold, and enable a first channel acquisition operation responsiveto determining that the signal parameter exceeds the predeterminedthreshold.

In accordance with yet another aspect of the present invention, atelevision signal receiver is disclosed. According to an exemplaryembodiment, the television signal receiver comprises a tuner operativeto tune a first frequency channel. A processor is operative to determinewhether a signal parameter associated with the first frequency channelexceeds a predetermined threshold. A first demodulator is operative toperform a first channel acquisition operation responsive to theprocessor determining that the signal parameter exceeds thepredetermined threshold.

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a block diagram of an exemplary apparatus suitable forimplementing the present invention; and

FIG. 2 is a flowchart illustrating steps according to an exemplaryembodiment of the present invention.

The exemplifications set out herein illustrate preferred embodiments ofthe invention, and such exemplifications are not to be construed aslimiting the scope of the invention in any manner.

Referring now to the drawings, and more particularly to FIG. 1, a blockdiagram of an exemplary apparatus 100 suitable for implementing thepresent invention is shown. For purposes of example and explanation,apparatus 100 represents a portion of a television signal receiver.However, it will be intuitive to those skilled in the art that theprinciples of the present invention may be applied to other apparatusesor devices, such as those used in a frequency division multiplexing(FDM) system.

Apparatus 100 comprises tuning means such as tuner 10 which includestunable filter means such as tunable bandpass filter 12, radio frequency(RF) amplification means such as RF amplifier 14, signal mixing meanssuch as signal mixer 16, and tunable oscillation means such as tunableoscillator 18. Apparatus 100 further comprises signal splitting meanssuch as signal splitter 20, intermediate frequency (IF) filtering meanssuch as fixed IF bandpass filters 22 and 24, IF amplification means suchas IF amplifiers 26 and 28, automatic gain control (AGC) means such asAGC control block 30, analog demodulation means such as analogdemodulation block 32, digital demodulation means such as digitaldemodulation block 34, processing means such as processor 36, and audioand/or video (A/V) processing means such as AN processing block 38. Theforegoing elements of apparatus 100 may for example be implemented usingintegrated circuits (ICs).

In FIG. 1, tuner 10 is operative to receive an RF input signal andperform a tuning operation thereon to thereby generate and output atuned IF signal. The RF input signal may be provided to tuner 10 via anywired or wireless signal source such as, but not limited to, a cable,terrestrial or satellite broadcast. For purposes of example, tuner 10 isshown in FIG. 1 as a single frequency conversion tuner. However, it willbe intuitive to those skilled in the art that the principles of thepresent invention may be applied to any tuner architecture.

With respect to tuner 10, tunable bandpass filter 12 is operative tofilter the RF input signal responsive to a control signal provided fromprocessor 36 to thereby generate and output a tuned RF signal. RFamplifier 14 is operative to amplify the tuned RF signal provided fromtunable bandpass filter 12 responsive to an RF gain control signalprovided from AGC control block 30 to thereby generate and output anamplified RF signal. Signal mixer 16 is operative to mix the amplifiedRF signal provided from RF amplifier 14 with an output frequency signalprovided from tunable oscillator 18 to thereby generate and output thetuned IF signal, which is nominally 44 MHz. Tunable oscillator 18generates the output frequency signal responsive to a control signalprovided from processor 36.

Signal splitter 20 is operative to split the tuned IF signal providedfrom tuner 10 into at least two different signal paths. Fixed IFbandpass filters 22 and 24 are operative to filter the tuned IF signalprovided from signal splitter 20 to thereby generate and output filteredIF signals. IF amplifiers 26 and 28 are operative to amplify thefiltered IF signals provided from fixed IF bandpass filters 22 and 24,respectively, responsive to an IF gain control signal provided from AGCcontrol block 30 to thereby generate and output amplified IF signals.

AGC control block 30 is operative to perform various operations,including signal parameter detection and gain control operations.According to an exemplary embodiment, AGC control block 30 includes adetector (not shown) such as a root mean squared (RMS) detector which isoperative to detect a signal parameter such as amplitude or otherparameter associated with the amplified IF signals provided from IFamplifiers 26 and 28. Also according to an exemplary embodiment, AGCcontrol block 30 provides the RF gain control signal to increase thegain of RF amplifier 14 as the detected amplitude of the incoming,amplified IF signals from IF amplifiers 26 and 28 drops. Once RFamplifier 14 has reached maximum gain, and the detected amplitude of theamplified IF signals continues to drop, AGC control block 30 thenprovides the IF gain control signal to increase the gains of IFamplifiers 26 and 28.

According to an exemplary embodiment, AGC control block 30 provides adigitized version of the IF gain control signal to processor 36 as anestimate of the amplitude of the incoming RF signal to tuner 10. As willbe described later herein, processor 36 compares the digitized IF gaincontrol signal to a predetermined threshold to determine whether acurrently tuned frequency channel likely includes a valid analog ordigital broadcast channel. According to the present invention, channelacquisition operations are not initiated for a given frequency channeluntil the predetermined threshold is exceeded. In this manner, channeldetection according to the present invention can be performedsubstantially faster than conventional channel detection techniquessince channel acquisition operations are not initiated until there is areasonable degree of certainty that a valid analog or digital broadcastchannel is present on a given frequency channel. Further detailsregarding these aspects of the present invention will be provided laterherein.

Analog demodulation block 32 is operative to perform various operations,including analog channel acquisition and demodulation operations.According to an exemplary embodiment, analog demodulation block 32initiates an analog channel acquisition operation upon the amplified IFsignal provided from IF amplifier 26 responsive to a control signalprovided from processor 36 to thereby determine whether a valid analogbroadcast channel is present on a currently tuned frequency channel.Analog demodulation block 32 provides a signal indicating the result ofthis determination back to processor 36. According to an exemplaryembodiment, analog demodulation block 32 performs the analog channelacquisition operation to acquire an NTSC channel, although other typesof analog channels (e.g., PAL, SECAM, etc.) may also be accommodatedaccording to the present invention. Analog demodulation block 32 is alsooperative to demodulate the amplified IF signal provided from IFamplifier 26 to thereby generate and output a demodulated analog signal.

Digital demodulation block 34 is operative to perform variousoperations, including digital channel acquisition and demodulationoperations. According to an exemplary embodiment, digital demodulationblock 34 initiates a digital channel acquisition operation upon theamplified IF signal provided from IF amplifier 28 responsive to acontrol signal provided from processor 36 to thereby determine whether avalid digital broadcast channel is present on a currently tunedfrequency channel. Digital demodulation block 34 provides a signalindicating the result of this determination back to processor 36.According to an exemplary embodiment, digital demodulation block 34performs the digital channel acquisition operation to acquire an ATSCchannel, although other types of digital channels (e.g., ISDB-T, DVB-T,DVB-C, etc.) may also be accommodated according to the presentinvention. Digital demodulation block 34 is also operative to demodulatethe amplified IF signal provided from IF amplifier 28 to therebygenerate and output a demodulated digital signal.

Processor 36 is operative to perform various operations, includingmemory, threshold detection, channel acquisition control, and frequencycontrol operations. According to an exemplary embodiment, processor 36is operative to compare the digitized IF gain control signal providedfrom AGC control block 30 to a predetermined threshold to determinewhether a currently tuned frequency channel likely includes a validanalog or digital broadcast channel. The actual threshold used byprocessor 36 in this operation is a matter of design choice, and may bebased on one or more factors associated with a particular application,such as the type of signal modulation and/or the signal source.Moreover, the threshold used by processor 36 may vary during aparticular channel scan operation based on factors such as signalmodulation and/or signal source.

With respect to signal modulation for example, an 8 level digitalvestigial sideband (8-VSB) modulated signal may require asignal-to-noise ratio (SNR) greater than 15 dB to produce a usablesignal. As another example, a 256 level digital quadrature amplitudemodulated (256-QAM) signal may require a SNR greater than 27 dB toproduce a usable signal. Accordingly, the threshold used for a 256-QAMapplication may for example be set 12 dB higher than the threshold usedfor an 8-VSB application. Analog modulation, such as NTSC modulation,may have other requirements such as maintaining peak power constant overtime, and therefore may use a threshold based on other designconsiderations.

With respect to signal source, cable television standards typically usewell-defined signal power levels that are substantially higher than thesignal power levels found in a terrestrial broadcast system.Accordingly, the threshold used for a cable application may besubstantially higher than the threshold used for a terrestrialapplication. According to an exemplary embodiment, the threshold usedmay be the lowest common denominator for various applications if asimpler, but less effective implementation is acceptable. In any event,the actual threshold used by processor 36 is a matter of design choice,and may be selected appropriately for a given application.

According to an exemplary embodiment, processor 36 enables channelacquisition operations to be performed only when the digitized IF gaincontrol signal provided from AGC control block 30 exceeds thepredetermined threshold. As previously indicated herein, processor 36 isoperative to provide control signals to analog and digital demodulationblocks 32 and 34 to initiate analog and digital channel acquisitionoperations, respectively. As will be discussed later herein, processor36 may also cause tuner 10 to tune another frequency channel whencertain conditions are satisfied, such as when the digitized IF gaincontrol signal provided from AGC control block 30 does not exceed thepredetermined threshold.

AN processing block 38 is operative to process the demodulated analogand digital signals provided from analog and digital demodulation blocks32 and 34, respectively, to thereby generate and provide AN outputs.According to an exemplary embodiment, AN processing block 38 isoperative to digitize and process the demodulated analog signal providedfrom analog demodulation block 32, which may for example be an NTSCsignal or other type of analog signal. Also according to an exemplaryembodiment, AN processing block 38 is operative to process thedemodulated digital signal provided from digital demodulation block 34,which may for example be an ATSC signal or other type of digital signal.

To facilitate a better understanding of the inventive concepts of thepresent invention, a more specific example will now be provided.Referring to FIG. 2, a flowchart 200 illustrating steps according to anexemplary embodiment of the present invention is shown. For purposes ofexample and explanation, the steps of FIG. 2 will be described withreference to apparatus 100 of FIG. 1. The steps of FIG. 2 are merelyexemplary, and are not intended to limit the present invention in anymanner.

At step 201, a channel scan operation is initiated. According to anexemplary embodiment, the channel scan operation may be performed inresponse to a user input to apparatus 100, such as via a remote controldevice (not shown in FIG. 1). The channel scan operation may for examplebe part of a user setup process for apparatus 100. As will be describedhereafter, the channel scan operation involves sequentially tuningdifferent frequency channels to detect the analog and/or digitalbroadcast channels available in a given area.

Different types of channel scan operations may be performed according tothe present invention. For example, one type of channel scan operation(e.g., a quick scan) may be performed for a particular RF input (e.g.,antenna A, antenna B, etc.) and/or signal source (e.g., cable,terrestrial, satellite, etc.) selected by a user. Another type ofchannel scan operation (e.g., a full scan) may for example be performedfor all available RF inputs and all available signal sources. Othertypes of channel scan operations may also be performed according to thepresent invention.

At step 202, a frequency channel is tuned. According to an exemplaryembodiment, tuner 10 tunes a frequency channel responsive to controlsignals provided to tunable bandpass filter 12 and tunable oscillator 18from processor 36. Also according to an exemplary embodiment, thefrequency channel tuned at step 202 is from a predetermined channel listused by processor 36 when performing the channel scan operation.

At step 203, a determination is made as to whether a signal parameterassociated with the frequency channel tuned at step 202 exceeds apredetermined threshold. According to an exemplary embodiment previouslydescribed herein, AGC control block 30 is operative to provide adigitized version of the IF gain control signal to processor 36 as anestimate of the amplitude of the incoming RF signal to tuner 10. Withthis exemplary embodiment, processor 36 compares the digitized IF gaincontrol signal to the predetermined threshold (which is a matter ofdesign choice) and thereby determines whether the threshold is exceeded,at step 203.

If the determination at step 203 is negative, process flow advances tostep 204 where a determination is made by processor 36 as to whether theend of the channel list has been reached. If the determination at step204 is positive, process flow advances to step 205 where the processends.

If the determination at step 204 is negative, process flow advances tostep 206 where processor 36 increments the current frequency channel tothe next (e.g., higher) frequency channel. Process flow then loops backto step 202 where processor 36 provides control signals to tunablebandpass filter 12 and tunable oscillator 18 of tuner 10 to thereby tunethe next frequency channel.

If the determination at step 203 is positive, process flow advances tostep 207 where a digital channel acquisition operation is initiated.According to an exemplary embodiment, the digital channel acquisitionoperation includes acquisition of a digital broadcast channel, such asan ATSC channel or other type of digital broadcast channel. Alsoaccording to an exemplary embodiment, processor 36 provides a controlsignal to digital demodulation block 34 to initiate the digital channelacquisition operation, which may include known operations such as tryingto achieve carrier synchronization, symbol timing synchronization, andequalization lock on the amplified IF signal provided from IF amplifier28. Other types of digital channel acquisition operations may also beperformed according to the present invention.

Next, at step 208, a determination is made as to whether a valid digitalbroadcast channel is detected from the digital channel acquisitionoperation initiated at step 207. According to an exemplary embodiment,digital modulation block 34 provides a control signal to processor 36indicating whether a valid digital broadcast channel is detected, namelywhether carrier, symbol timing, and equalization lock is achieved on theamplified IF signal provided from IF amplifier 28.

If the determination at step 208 is positive, process flow advances tostep 209 where processor 36 adds the detected digital broadcast channelto a list of valid broadcast channels. Next, at step 210, adetermination is made by processor 36 as to whether the end of thechannel list has been reached. If the determination at step 210 ispositive, process flow advances to step 211 where the process ends.

If the determination at step 210 is negative, process flow loops back tostep 206, where processor 36 increments the current frequency channel tothe next (e.g., higher) frequency channel. Process flow then loops backto step 202 where processor 36 provides control signals to tunablebandpass filter 12 and tunable oscillator 18 of tuner 10 to thereby tunethe next frequency channel.

If the determination at step 208 is negative, process flow advances tostep 212 where an analog channel acquisition operation is initiated.According to an exemplary embodiment, the analog channel acquisitionoperation includes acquisition of an analog broadcast channel, such asan NTSC channel or other type of analog broadcast channel. Alsoaccording to an exemplary embodiment, processor 36 provides a controlsignal to analog demodulation block 32 to initiate the analog channelacquisition operation, which may include performing known operationssuch as automatic fine tuning (AFT) crossover and/or horizontalsynchronization detection operations on the amplified IF signal providedfrom IF amplifier 26. Other types of analog channel acquisitionoperations may also be performed according to the present invention.

Next, at step 213, a determination is made as to whether a valid analogbroadcast channel is detected from the analog channel acquisitionoperation initiated at step 212. According to an exemplary embodiment,analog modulation block 32 provides a control signal to processor 36indicating whether a valid analog broadcast channel is detected, namelywhether the AFT crossover and/or horizontal synchronization detectionoperations are successfully performed on the amplified IF signalprovided from IF amplifier 26.

If the determination at step 213 is positive, process flow loops back tostep 209 where processor 36 adds the detected analog broadcast channelto the list of valid broadcast channels. Process flow then advances tostep 210 and continues in the manner previously described herein, asindicated in FIG. 2. If the determination at step 213 is negative,process flow loops back to step 210 and continues in the mannerpreviously described herein, as indicated in FIG. 2. Once the steps ofFIG. 2 are repeated for all frequency channels of the channel list, theresultant list of valid broadcast channels may be used to enable channelselection by a user.

Numerous variations of FIG. 2 may also be performed according to thepresent invention. For example, FIG. 2 shows the digital channelacquisition operation being performed before the analog channelacquisition operation (see steps 207 and 212). In practice, however, itmay be desirable to perform the analog channel acquisition operationbefore the digital channel acquisition operation. For example, incertain cable applications, channel detection may be performed morerapidly if the analog channel acquisition operation is performed beforethe digital channel acquisition operation. Accordingly, the order inwhich the digital and analog channel acquisition operations areperformed is a matter of design choice.

According to another variation of FIG. 2, certain channel scanoperations may utilize a plurality of different predetermined thresholds(see step 203). For example, when performing a channel scan operationfor a particular signal source (e.g., digital cable broadcast source,etc.), a particular frequency channel may be searched for signals havingdifferent types of signal modulation (e.g., 8-VSB, 64-QAM, 256-QAM,etc.), and a different predetermined threshold may be used for each typeof signal modulation. Accordingly, the predetermined threshold usedduring a particular channel scan operation may vary based on factorssuch as signal source (e.g., cable, terrestrial, satellite, etc.) and/orsignal modulation. Other variations of FIG. 2 may also be performedaccording to the present invention.

As described herein, the present invention provides a technique forperforming channel detection in devices such as a television signalreceiver that is capable of quickly determining the analog and/ordigital broadcast channels available in a given area. In particular, itis noted that a given channel acquisition operation may take anywherefrom 500 to 2000 milliseconds to fail, depending on the particularimplementation. In contrast, the process of determining whether a signalparameter such as amplitude associated with a given frequency channelexceeds a predetermined threshold (i.e., see step 203) may take no morethan 200 milliseconds. Accordingly, by performing this step beforeinitiating any channel acquisition operations, the present inventionsaves a substantial amount of time as compared to conventional channeldetection techniques.

The present invention is particularly applicable to various apparatuses,either with or without a display device. Accordingly, the phrase“television signal receiver” as used herein may refer to systems orapparatuses including, but not limited to, television sets, computers ormonitors that include a display device, and systems or apparatuses suchas set-top boxes, video cassette recorders (VCRs), digital versatiledisk (DVD) players, video game boxes, personal video recorders (PVRs),computers or other apparatuses that may not include a display device.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1. A method for performing channel detection, comprising: tuning a firstfrequency channel; determining whether a signal parameter associatedwith said first frequency channel exceeds a predetermined threshold; andenabling a first channel acquisition operation responsive to determiningthat said signal parameter exceeds said predetermined threshold.
 2. Themethod of claim 1, further comprised of enabling a second channelacquisition operation after enabling said first channel acquisitionoperation.
 3. The method of claim 2, wherein: said first channelacquisition operation includes acquisition of a digital broadcastchannel; and said second channel acquisition operation includesacquisition of an analog broadcast channel.
 4. The method of claim 3,wherein: said digital broadcast channel is an ATSC channel; and saidanalog broadcast channel is an NTSC channel.
 5. The method of claim 2,wherein: said first channel acquisition operation includes acquisitionof an analog broadcast channel; and said second channel acquisitionoperation includes acquisition of a digital broadcast channel.
 6. Themethod of claim 5, wherein: said analog broadcast channel is an NTSCchannel; and said digital broadcast channel is an ATSC channel.
 7. Themethod of claim 1, further comprised of tuning a second frequencychannel responsive to determining that said signal parameter does notexceed said predetermined threshold
 8. The method of claim 1, whereinsaid signal parameter includes amplitude.
 9. The method of claim 1,wherein said predetermined threshold varies based on signal source. 10.The method of claim 1, wherein said predetermined threshold varies basedon signal modulation.
 11. An apparatus for performing channel detection,comprising: tuning means for tuning a first frequency channel; andprocessing means for determining whether a signal parameter associatedwith said first frequency channel exceeds a predetermined threshold, andfor enabling a first channel acquisition operation responsive todetermining that said signal parameter exceeds said predeterminedthreshold.
 12. The apparatus of claim 11, wherein said processing meansfurther enables a second channel acquisition operation after enablingsaid first channel acquisition operation.
 13. The apparatus of claim 12,wherein: said first channel acquisition operation includes acquisitionof a digital broadcast channel; and said second channel acquisitionoperation includes acquisition of an analog broadcast channel.
 14. Theapparatus of claim 13, wherein said digital broadcast channel is an ATSCchannel; and said analog broadcast channel is an NTSC channel.
 15. Theapparatus of claim 12, wherein: said first channel acquisition operationincludes acquisition of an analog broadcast channel; and said secondchannel acquisition operation includes acquisition of a digitalbroadcast channel.
 16. The apparatus of claim 15, wherein: said analogbroadcast channel is an NTSC channel; and said digital broadcast channelis an ATSC channel.
 17. The apparatus of claim 11, wherein said tuningmeans tunes a second frequency channel responsive to said processingmeans determining that said signal parameter does not exceed saidpredetermined threshold.
 18. The apparatus of claim 11, wherein saidsignal parameter includes amplitude.
 19. The apparatus of claim 11,wherein said predetermined threshold varies based on signal source. 20.The apparatus of claim 11, wherein said predetermined threshold variesbased on signal modulation.
 21. A television signal receiver,comprising: a tuner operative to tune a first frequency channel; aprocessor operative to determine whether a signal parameter associatedwith said first frequency channel exceeds a predetermined threshold; anda first demodulator operative to perform a first channel acquisitionoperation responsive to said processor determining that said signalparameter exceeds said predetermined threshold.
 22. The televisionsignal receiver of claim 21, further comprising a second demodulatoroperative to perform a second channel acquisition operation after saidfirst demodulator performs said first channel acquisition operation. 23.The television signal receiver of claim 22, wherein: said first channelacquisition operation includes acquisition of a digital broadcastchannel; and said second channel acquisition operation includesacquisition of an analog broadcast channel.
 24. The television signalreceiver of claim 23, wherein: said digital broadcast channel is an ATSCchannel; and said analog broadcast channel is an NTSC channel.
 25. Thetelevision signal receiver of claim 22, wherein: said first channelacquisition operation includes acquisition of an analog broadcastchannel; and said second channel acquisition operation includesacquisition of a digital broadcast channel.
 26. The television signalreceiver of claim 25, wherein: said analog broadcast channel is an NTSCchannel; and said digital broadcast channel is an ATSC channel.
 27. Thetelevision signal receiver of claim 21, wherein said tuner is furtheroperative to tune a second frequency channel responsive to saidprocessor determining that said signal parameter does not exceed saidpredetermined threshold.
 28. The television signal receiver of claim 21,wherein said signal parameter includes amplitude.
 29. The televisionsignal receiver of claim 21, wherein said predetermined threshold variesbased on signal source.
 30. The television signal receiver of claim 21,wherein said predetermined threshold varies based on signal modulation.